Device providing electrical contact to the surface of a semiconductor workpiece during processing

ABSTRACT

Substantially uniform deposition of conductive material on a surface of a substrate, which substrate includes a semiconductor wafer, from an electrolyte containing the conductive material can be provided by way of a particular device which includes first and second conductive elements. The first conductive element can have multiple electrical contacts, of identical or different configurations, or may be in the form of a conductive pad, and can contact or otherwise electrically interconnect with the substrate surface over substantially all of the substrate surface. Upon application of a potential between the first and second conductive elements while the electrolyte makes physical contact with the substrate surface and the second conductive element, the conductive material is deposited on the substrate surface. It is possible to reverse the polarity of the voltage applied between the anode and the cathode so that electro-etching of deposited conductive material can be performed.

RELATED APPLICATIONS

[0001] This is a continuation of U.S. Ser. No. 10/302,213 filed Nov. 22,2002 which is a continuation of U.S. Ser. No. 09/685,934 filed Oct. 11,2000 now U.S. Pat. No. 6,497,800 claiming priority to U.S. Prov. No.60/190,023, filed Mar. 17, 2000, all incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Multi-level integrated circuit (IC) manufacturing requires manysteps of metal and insulator film depositions followed by photoresistpatterning and etching or other means of material removal. Afterphotolithography and etching, the resulting wafer or substrate surfaceis non-planar and contains many features such as vias, lines orchannels. Often, these features need to be filled with a specificmaterial such as a metal or other conductor. Once filled with aconductor, the features provide the means to electrically interconnectvarious parts of the IC.

[0003] Electrodeposition is a technique used in IC manufacturing for thedeposition of a highly conductive material, such as copper (Cu), intothe features on the semiconductor wafer surface. FIG. 1 is a schematicillustration of a wafer or substrate 16 to be coated with Cu. Features 1may be vias, trenches, bond pads, etc., and are opened in the dielectricor insulator layer 2. To achieve Cu deposition, a barrier layer 3 isfirst deposited over the whole wafer surface. Then, a conductive Cu seedlayer 4 is deposited over the barrier layer 3. An electrical contact ismade to the barrier layer 3 and/or the seed layer 4, the wafer surfaceis exposed to a Cu plating electrolyte, and a cathodic voltage isapplied to the wafer surface with respect to an anode which also makesphysical contact with the electrolyte. In this way, Cu is plated out ofthe electrolyte, onto the wafer surface, and into the features 1.

[0004] The terms “wafer” and “substrate” are used interchangeably aboveand throughout the remaining description. Referring to the example shownin FIG. 1, it is to be understood that the “wafer” or “substrate”referred to includes the wafer WF per se, the dielectric or insulatorlayer 2, and the barrier layer 3, with or without the seed layer 4.These terms, of course, may also refer to a wafer WF per se, includingone or more previously processed layers, a further dielectric orinsulator layer, and a further barrier layer, with or without a furtherseed layer.

[0005] The electrical contact to the seed layer and/or the barrier layeris typically made along the periphery of the wafer, which is usuallyround. This approach works well for thick and highly conductive seedlayers and small wafer diameters (e.g. 200 mm). However, the trend inthe semiconductor industry is to go to larger wafers (e.g. 300 mm) andsmaller feature sizes (smaller than 0.18 microns). Smaller featuresizes, as well as cost considerations, require the use of the thinnestpossible seed layers. As the wafer size increases, the plating currentvalue also increases. As the seed layer thickness decreases, the sheetresistance increases, and the voltage drop between the middle and theedge of a large wafer also increases. Therefore, voltage drop becomes amajor problem, especially for large wafers with thin seed layers. Thisvoltage drop results in non-uniform Cu deposition on the wafer surface,the regions near the contacts being typically thicker than otherregions.

[0006] One other consideration in Cu plating is the “edge exclusion”. Cuplating heads, such as the one described in commonly assigned, copendingapplication Ser. No. 09/472,523, filed Dec. 27, 1999, titled WORK PIECECARRIER HEAD FOR PLATING AND POLISHING, typically use contacts aroundperipheries of the wafers. Making electrical contact and, at the sametime, providing a seal against possible electrolyte leakage isdifficult.

[0007]FIG. 1 a shows a cross sectional view of a contacting scheme inwhich the wafer or substrate 16 is contacted by a ring-shaped contact 17which is sealed by a ring seal 18 against exposure to the electrolyte 9a. The seal 18 also prevents the electrolyte 9 a from reaching the backsurface of the wafer or substrate 16. Such a contacting scheme extends adistance “W” from the edge of the wafer. The distance “W” is referred toas “edge exclusion” and may typically be 3-7 mm. Minimizing “W” wouldallow better utilization of the wafer surface for IC fabrication.

[0008] There is, therefore, a need to develop new and novel approachesto provide electrical contacts to the surface of semiconductor wafersduring electrodeposition of conductors.

SUMMARY OF THE INVENTION

[0009] It is a primary object of this invention to provide both a deviceand a method by which substantially uniform deposition of conductivematerial on a surface of a substrate, which includes a semiconductorwafer, from an electrolyte containing the conductive material is madepossible. According to the invention, a first conductive element cancontact or otherwise electrically interconnect with the substratesurface at locations disposed over substantially all of the surface.Upon application of a potential between the first conductive element anda second conductive element, while the electrolyte makes physicalcontact with the surface and the second conductive element, theconductive material is deposited on the surface.

[0010] In one preferred form of the invention, the first conductiveelement is provided with multiple electrical contacts. The multipleelectrical contacts may include pins extending from the first conductiveelement, rollers biased and electrically interconnected, at least inpart, by springs with the first conductive element, or variouscombinations of such pin and spring biased roller contacts. In this formof the invention, the first conductive element is a cathode plate, andthe second conductive element is an anode plate. Each pin or springbiased roller contact extends through a hole provided in the secondconductive element, and an insulator is interposed between the pin orthe spring biased roller contact and the second conductive element. Theelectrical contacts are biased into contact or at least into electricalconnection with the substrate surface. The device also includes a paddisposed on the second conductive element by which the substrate surfacecan be polished. At least one of the substrate and the second conductiveelement can be moved relative to the other while the conductive materialis deposited on the surface of the substrate. This relative movement maybe in the form of rotation and/or translation. If pins are used as theelectrical contacts, each pin may have a rounded tip adapted to contactthe substrate surface.

[0011] In another preferred form of the invention, the first conductiveelement can be a conductive pad through which the electrolyte can flow,and the second conductive element can be an anode plate separated by aninsulating spacer from the conductive pad. At least one of the substrateand the pad can be rotated or translated relative to the other while theconductive material is deposited on the surface of the substrate, and inthis way the substrate surface can be polished by the pad.

[0012] The device can also be used to provide substantially uniformelectro-etching of conductive material deposited on the substratesurface when the polarity of the potential applied is reversed.Moreover, the device can be used simply to provide substantially uniformelectro-etching of conductive material on the substrate surface. In thiscase, a first conductive element can be electrically interconnected withthe substrate surface over substantially all of the surface. Uponapplication of a potential between the first and second conductiveelements while an electrolyte makes physical contact with the surface ofthe substrate and the second conductive element, the conductive materialon the surface will be etched.

[0013] Other features and advantages of the invention will becomeapparent from the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is an illustration of the known structure of a wafer orsubstrate to be coated with Cu.

[0015]FIG. 1a is a cross sectional side view of a wafer or substratecontacting scheme.

[0016]FIG. 2 is a schematic illustration of an apparatus in which thepresent invention may be utilized.

[0017]FIG. 3 shows one electrical contact embodiment in a device formingthe subject matter of the present invention.

[0018]FIG. 4 shows another electrical contact embodiment.

[0019]FIG. 5 is a cross sectional side view similar to FIG. 1a butshowing a reduction in wafer edge exclusion made possible by theinvention.

[0020]FIGS. 6a, 6 b, and 6 c show various individual electrical contactdistributions.

[0021]FIG. 7 shows another electrical contact embodiment.

[0022]FIG. 8 shows a further electrical contact embodiment.

[0023]FIG. 9 shows still another electrical contact embodiment.

[0024]FIG. 10 shows one more electrical contact embodiment.

[0025]FIG. 11 is a schematic illustration of a single electrical contactsuch as that shown in FIG. 10 while in contact with a wafer surfaceduring application of an electric field.

[0026]FIG. 12 shows part of another electrical contact embodiment whichis similar to those of FIGS. 9 and 10 but in which a roller and a rollersupport member have different sizes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The following is a description of novel approaches to makedistributed multiple electrical contact to the wafer surface, all overthe surface, rather than just at the periphery. Various approaches aredescribed.

[0028] A general depiction of one version of a plating apparatus isshown in FIG. 2. This apparatus can also be used for plating andpolishing as disclosed in commonly assigned application Ser. No.09/201,929, filed Dec. 1, 1998, titled METHOD AND APPARATUS FORELECTROCHEMICAL MECHANICAL DEPOSITION, and commonly assigned, copendingapplication Ser. No. 09/472,523, filed Dec. 27, 1999, titled WORK PIECECARRIER HEAD FOR PLATING AND POLISHING. The carrier head 10 holds thewafer 16. The wafer has the barrier layer and the seed layer (not shownin FIG. 2) deposited on its surface, and therefore its surface isconductive. The head can be rotated around a first axis 10 b. It canalso be moved in the x, y, and z directions. A pad 8 is placed on ananode plate 9 across from the wafer surface. The pad surface may itselfbe abrasive, or the pad may contain an abrasive material. Pad designsand structures form the subject matter of commonly assigned, copendingapplication Ser. No. 09/511,278, filed Feb. 23, 2000, titled PAD DESIGNSAND STRUCTURES FOR A VERSATILE MATERIALS PROCESSING APPARATUS, andcommonly assigned, copending application Ser. No. 09/621,969, filed Jul.21, 2000, titled PAD DESIGNS AND STRUCTURES WITH IMPROVED FLUIDDISTRIBUTION.

[0029] Electrolyte 9 a is supplied to the wafer surface through theopenings in the anode plate and the pad as shown by the arrows in FIG.2. Commonly assigned, copending application Ser. No. 09/568,584, filedMay 11, 2000, titled ANODE ASSEMBLY FOR PLATING AND PLANARIZING ACONDUCTIVE LAYER, discloses an anode plate, while commonly assigned,copending application Ser. No. 09/544,558, filed Apr. 6, 2000, titledMODIFIED PLATING SOLUTION FOR PLATING AND PLANARIZATION, the disclosureof which is incorporated by reference herein as non-essential material,discloses an electrolyte. The electrolyte then flows over the edges ofthe pad into the chamber 9 c to be re-circulated aftercleaning/filtering/refurbishing. An electrical contact 9 d is providedto the anode plate. The anode plate turns around the axis 10 c. In someapplications, the plate may also be translated in the x, y, and/or zdirections. Axes 10 b and 10 c are substantially parallel to each other.The diameter of the pad 8 is typically smaller than the diameter of thewafer surface exposed to the pad surface, although it may also belarger. The gap between the wafer surface and the pad is adjustable bymoving the carrier head and/or the anode plate in the z direction. Inone mode of operation, the workpiece (i.e., the wafer or substrate) maybe brought close to the pad, without touching the pad. In this mode,during material deposition, the workpiece hydroplanes or floats over thepad or anode. In another mode of operation, the wafer surface and thepad may be in contact. When the wafer surface and the pad are touching,the pressure that is exerted on the wafer and pad surfaces can also beadjusted.

[0030] According to a first embodiment of the invention, electricalconnection to the wafer surface is made by way of multiple electricalcontacts formed by pins that come up through the pad 8 and touch thewafer surface. Assuming by way of example that it is the structure shownin FIG. 1 that is to be plated, and referring now to FIG. 3, it will beunderstood that the wafer surface 22 is formed by the exposed surface ofthe seed layer 4. A magnified view of one of the multiple electricalcontacts is shown in FIG. 3. Holes 24 have been provided in the anodeplate 9 to accommodate the pins 20. These pins 20 are electricallyisolated from the anode plate 9 by an insulator 26. The insulator may bea ceramic or other appropriate dielectric material. A seal 25 isinterposed between the anode plate 9 and the insulator 26. The pins 20forming the electrical contacts are an integral part of a cathode plate30, which is also electrically isolated from the anode plate 9 by theinsulator 26. The cathode plate 30 is spring loaded by suitable springs32 which bias or push the rounded tips 20T of the pins 20 towards thewafer surface 22 during the plating operation. Thus, the electricalcontacts can slide up under the spring bias and down against the springbias to adjust dynamically to the carrier head or workpiece locationrelative to the anode plate.

[0031] A roller ball, similar to that which could be used in aball-point pen, can be incorporated at the tips 20T to preventscratching the wafer surface. Various additional or alternativeelectrical contact configurations will be described in connection withFIGS. 7-12. Soft conductive brushes can also be used to make contact tothe wafer surface. It is important that the selected contacts do notscratch the wafer surface excessively.

[0032] For plating, the electrolyte 9 a is supplied to the gap 34between the pad 8 and the wafer surface 22 and thus is brought intophysical contact with the wafer surface and the anode plate. In one modeof operation, the wafer 16 is brought down until its surface 22 makesphysical contact to the tips 20T of the pins 20. A potential is appliedbetween the cathode plate 30 and the anode plate 9, making the cathodeplate 30 more negative than the anode plate 9. Therefore, the wafersurface is also rendered cathodic through the pins 20. Under appliedpotential, copper plates out of the electrolyte 9 a onto the wafersurface 22. By adjusting the gap 34 between the pad 8 and the wafersurface 22 and/or by adjusting the pressure with which the pad 8 and thewafer surface 22 touch each other, one can achieve just plating, orplating and polishing. For effective polishing it is preferred that thepad 8 have an abrasive surface or that the whole pad 8 is abrasive.

[0033] During plating, the wafer or substrate 16 and the anode plate/padassembly 8, 9 should rotate with respect to one another so that platingtakes place uniformly. They may also translate in one or two directions.The electrolyte 9 a typically fills any gap 34 between the pad 8 and thewafer surface 22. It is most preferable that the electrolyte 9 a beapplied through channels in the anode plate 9 and the pad 8 (not shownin FIG. 3). Alternately, if the gap 34 is large (e.g. 2 mm or larger),the electrolyte can be provided into the gap 34 from the edges of thewafer.

[0034] In other applications, the pin tips 20T, or the tips of othertypes of electrical contacts which will be described, may be disposed inclose proximity to the wafer surface 22 without touching this surface.Moreover, under a potential applied between the wafer and the anodeplate, copper may be either plated onto or removed from the wafer,depending on the polarity of the wafer. Circuitry used for applicationand adjustment of the applied potential, and for inverting the polarityof the potential, is well known and commonly used.

[0035] In the construction shown in FIG. 4, electrical contact to thewafer surface is made by way of a potential conductive pad 80. This pad80 is used in place of the multiple pins 20. In this case, an insulatingspacer 82 of ceramic or other dielectric material is placed directlyover the anode plate 9′ between the anode plate 9′ and the conductivepad 80. Electrical supply contacts are made to the conductive pad 80 andthe anode plate 9′, and a cathodic potential is applied to the pad 80,with electrolyte 9 a making physical contact to the anode plate 9′, thepad 80 and the wafer surface 22. When the substrate or wafer 16 isbrought down and engages the pad, it gets energized and Cu plating onthe wafer surface 22 commences. The construction shown in FIG. 4 issimilar to certain pad designs and structures forming the subject matterof application Ser. No. 09/511,278, filed Feb. 23, 2000, mentionedpreviously. Additionally, commonly assigned application Ser. No.09/483,095, filed Jan. 14, 2000, titled SEMICONDUCTOR WORKPIECEPROXIMITY PLATING METHODS AND APPARATUS, discloses conductive pad stripsused on cylindrical anodes. In other applications, the potentialconductive pad 80 may be allowed to float with respect to the wafersurface 22 during material deposition or removal. The potential,moreover, may be pulsed to produce impulse plating. Again, the circuitryused for pulsing the potential is well known and commonly used.

[0036] In both approaches described above and in others which will bedescribed, some Cu plating may take place on the exposed cathodicsurfaces besides the wafer surface. In the case of pins, for example,exposed regions of the pins may get coated. In case of a conductive pad,the whole pad may get coated. Therefore, it is of utmost importance toselect the right conductive materials to be used for the construction ofthe electrical contacts and the pads. The materials should be such thatplating on the Cu coated wafer surface (i.e. the seed layer 4 of FIG. 1)should be preferable or more efficient than plating on the pad orcontact surface. Examples of proper materials for the pads may bevarious conductive polymers or polymeric materials that are coated withrefractory metals such as Ta, alpha Ta, W, Mo or their nitrides. Thepins or other electrical contacts can be made of conductive polymers orrefractory metals such as Mo, Ta and W; alternatively, the pins or othercathode contacts can be made of any conductive metal such as Cu or Ni,or of a conductive alloy such as Cu—Be, Cu—Ag, Ag—Pt, etc., but thesemetals or alloys may be coated by a refractory metal or compound and/ora nitride of a refractory metal, such as TaN or TiN, or of a refractorycompound. These are just some examples. There are many more materials onwhich Cu does not deposit efficiently.

[0037] By employing this invention, the “edge exclusion” discussedearlier in connection with FIG. 1a can be reduced on the wafer. As shownin FIG. 5, eliminating the need for a contact ring to contact theperiphery of the wafer permits a reduction of the edge exclusion “d”.The seal 18 can be either on the surface 22 of the wafer 16 facing theelectrolyte 9 a or right at the edge 16 a of the wafer. The seal 18 mayeven be disposed on the surface 35 of the wafer 16 facing away from theelectrolyte 9 a.

[0038] Various electrical contact distributions may be used. FIGS. 6a-6c schematically show three possible types of distribution of pins 20over a cathode plate 30. As a rule, as the number of electrical contactsincreases, the voltage drop from the center to the edge of the waferwill become smaller, and the thickness of the plated metal becomes moreuniform.

[0039] Thus far, the invention has been described using Cu as the platedmetal. However, practically any metal or conductive alloy can be platedon a wafer/substrate surface using this invention.

[0040] Although the invention has been described with reference to anelectroplating technique and apparatus, it is also directly applicableto electroetching and/or electro-polishing techniques and apparatus. Inthis case, the polarity of the voltage applied between the anode andcathode plates is reversed, making the substrate surface more positive.An electro-etching electrolyte may be used. Again, the circuitry usedfor application and adjustment of the voltage, and for inversion of thevoltage polarity, is well known and commonly used.

[0041]FIG. 7 shows one of a plurality of electrical contacts which maybe used as alternatives to, or together with, pins such as the pins 20,or together with other electrical contact configurations, to provide thenecessary electrical connection to a wafer surface. FIGS. 8-10 and 12also show additional electrical contact configurations which can be usedas alternatives to, or together with, other contact configurations. Eachelectrical contact of FIG. 7 includes a conductive roller 120, which ispreferably spherical in geometry. Rollers having other suitablegeometrical shapes, such as cylindrical rollers, may be used. Therollers are preferably coated with a corrosion resistant material suchas gold, platinum, pallidum, their alloys, or some other appropriatecontact alloy material.

[0042] The roller 120 may be housed in an arrangement that may include,but is not limited to, a contact spring 122 to supply electrical powerfrom the cathode plate (not shown) to the roller 120. The end of thespring 122 also acts as a bearing surface. The spring 122 allows for agentle but dynamic loading of the roller 120 on the surface of theworkpiece. Each spring 122 biases its respective roller toward the wafersurface. In the embodiment shown in FIG. 7, the electrical contact perse is formed by the roller 120 and the spring 122 which supports theroller. Each spring 122 extends between the cathode plate (not shown inFIG. 7), on which the spring is supported in any appropriate fashion,and the roller 120 supported by the spring. Both the spring 122 and theroller 120 are surrounded by an insulator 124 of a ceramic or otherappropriate dielectric material that isolates the spring 122 and theroller 120 from an electric field during the process of plating Cu outof the electrolyte. The insulator 124 may be configured similarly to theinsulator 26, represented in FIG. 1, but can include a shaped tip 128.The shaped tip 128 and a seal 126 are disposed around the roller 120.The seal 126 may be adhesively or otherwise secured to the inner surfaceof the shaped tip.

[0043] The seal arrangement is such that the roller 120 rotates freelywith respect to the seal 126. The electrolyte fluid boundary layer, and,if the electrolyte forming the subject matter of copending applicationSer. No. 09/544,558 mentioned above is used, especially the additive inthe electrolyte, helps lubricate the roller surface. In addition tohousing the roller 120 and the seal 126, the tip 128 also prevents theroller 120 from exposure to the electric field. FIG. 11, which shows oneelectrical contact according to another embodiment in use, indicates anapplied electric field by reference characters E. Consequently, the tipand seal configuration helps prevent or minimize material deposition onthe roller 120.

[0044]FIG. 8 shows another embodiment in which a rolling pad 230 ofconducting material (e.g. metal), preferably with a partially sphericalshaped surface, is disposed between the contact spring 222 and aspherical roller 220. The roller 220 rests on the shaped rolling pad230. The shaped tip 228 and the seal 226 cooperate with the springbiased rolling pad 230 to confine the roller 220 while allowing it torotate freely along any direction. In a manner similar to the roller 120of FIG. 7, the roller 220 protrudes partly through but is restrained bythe perimeter of an end opening in the insulator 224 which surrounds theseal 226, the spring 222, and the rolling pad 230. In the embodimentshown in FIG. 8, therefore, the electrical contact per se is formed bythe roller 220, the spring 222, and the spring biased rolling pad 230disposed between the roller and the spring.

[0045]FIG. 9 shows that a conductive roller 320 may rest on a supportmember 330 having, for example, a spherical supporting surface ratherthan on a rolling pad. Multiple support members could be used beneaththe roller 320. Such an arrangement is ideal for self-aligned rollercontact. In the embodiment shown in FIG. 9, the electrical contact perse is formed by the roller 320, the spring 322, and the support member330.

[0046] Besides the advantage of self alignment, the rolling fictionbetween the roller 320 and the substrate or workpiece is greatlyreduced, especially when the workpiece rotates or translates during theprocess of plating Cu out of the electrolyte. The reduced frictionminimizes undesirable workpiece scratching and damage as well asparticulate generation.

[0047] Other suitable support member geometries could also be used. Forinstance the cross section of the support member may be triangular, orthe roller support may rest on the knife edge of a support member. Inanother embodiment, shown in FIG. 10, a spherical support 430 isdisposed between a conductive roller pad 432 and the roller 420. In FIG.10, the electrical contact per se is formed by the roller 420, theconductive spring 422, the conductive spherical support 430, and thespring biased and conductive rolling pad 432. FIG. 11 shows theembodiment of FIG. 10 in use during conductive material deposition.Also, as shown in FIG. 12, the size of the roller 520 may be differentfrom that of the roller support member 530.

[0048] It is important that the roller material, the contact springmaterial, and the like do not degrade or dissolve in the electrolyte ofinterest. It is also desirable that these materials do not degrade thequality of the material deposited. The roller, for example, must notexcessively scratch the deposited film or generate very undesirableparticulates. Numerous face contacts may be made around the periphery ofthe wafer. The individual contacts may be discrete and range from 4 toabout 2000 in number, depending on size of the substrate. As the size ofthe wafer or substrate increases, the number of electrical contacts usedshould also increase. The roller contacts could also be a continuousrace track or a track which is split into several elements. For example,the periphery may be divided into quadrants or octets. Each quadrant,etc., may contain many more or less uniformly dispersed roller contactsor contact tips.

[0049] Finally, although the invention is described with reference to anelectroplating technique and apparatus, it is directly applicable to anelectro-etching or electro-polishing technique or apparatus. In thiscase, the polarity of the voltage applied between the anode and cathodeplates is reversed, making the substrate surface more positive. Aspecial electro-etching electrolyte also could be used.

[0050] The foregoing disclosure has been set forth merely to illustratethe invention and is not intended to be limiting. Since modifications ofthe disclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

We claim:
 1. An apparatus for operating on a conductive surface of asubstrate using a solution, comprising: a carrier head assembly whichholds the substrate; a conductive pad assembly having a first electricalcontact; an electrode having a second electrical contact configured toreceive a potential difference applied to the first electrical contactand the second electrical contact to operate on the conductive surfaceof the substrate with the solution.
 2. The apparatus according to claim1, wherein the pad assembly includes an insulator configured toelectrically isolate the pad assembly from the electrode.
 3. Theapparatus according to claim 1, wherein the pad assembly includes aplurality of channels configured to flow the solution between theelectrode and the conductive surface of the substrate.
 4. The apparatusaccording to claim 3 wherein the plurality of channels is configured tofill a gap between the pad assembly and the substrate with the solution.5. The apparatus according to claim 1, wherein the solution platesconductive material to the conductive surface of the substrate inresponse to the potential difference.
 6. The apparatus according toclaim 1, wherein the conductive material is removed from the substratein response to the potential difference.
 7. The apparatus according toclaim 6, wherein the pad assembly includes an abrasive pad configured topolish the conductive surface of the substrate.
 8. The apparatusaccording to claim 1, wherein the carrier head assembly and the padassembly are configured to move relative to each other.
 9. The apparatusaccording to claim 8, wherein the carrier head assembly and the padassembly are configured to rotate relative to each other.
 10. Theapparatus according to claim 8, wherein the carrier head assembly andthe pad assembly are configured to translate relative to each other. 11.An article of manufacture for operating on a conductive surface of asubstrate comprising a conductive pad having at least one electricalcontact configured to conduct electrical power to the substrate.
 12. Thearticle of manufacture of claim 11, wherein the conductive pad includesat least one channel adapted to pass solution.
 13. The article ofmanufacture of claim 11, wherein the conductive pad includes a pluralityof apertures formed therethrough.
 14. The article of manufacture ofclaim 11, wherein the conductive pad includes a first surface having aninsulative spacer disposed thereon.
 15. The article of manufacture ofclaim 14, wherein the conductive pad includes a second surface having apolishing pad disposed thereon.
 16. The article of manufacture of claim11, wherein the conductive pad comprises refractory properties.
 17. Thearticle of manufacture of claim 11, wherein the conductive pad comprisesconductive polymers coated with refractory metals selected from thegroup consisting of Ta, alpha Ta, W, Mo, or their nitrides.
 18. Thearticle of manufacture of claim 11, wherein the at least one electricalcontact comprises a conductive material selected from the groupconsisting of Cu, Ni, Cu—Be, Cu—Ag, Ag—Pt, or combinations thereof. 19.The article of manufacture of claim 18, wherein the conductive materialis coated with a refractory material selected from the group consistingof a refractory metal, refractory compound, or nitride of a refractorymetal.
 20. The article of manufacture of claim 11, wherein theconductive pad includes soft conductive brushes.